Master Gardener - Ground pearls, not your lawn's best friend

Friday

May 24, 2013 at 8:02 AM

The most lethal pest of lawn grasses in our area is also one of the least well known.

By Charlotte Glen

The most lethal pest of lawn grasses in our area is also one of the least well known. Called ground pearl or pearl bugs, these insects can be found damaging lawns throughout coastal North Carolina. In yards infested with ground pearl, it is often impossible to maintain a healthy lawn since there are no effective treatments for this pest. Managing lawns infested with ground pearl instead relies on redesigning landscape beds to minimize turf areas, choosing turf grasses that better tolerate ground pearl and encouraging vigorous turf growth. Identifying the pestsLawns infested with ground pearl exhibit dead areas where little grows except a few weeds. These areas may be only a few inches across or up to several feet in size, depending on how widespread the ground pearl are. They are often roughly circular in shape. The dead areas expand slowly, by up to a foot each year. If grass is replanted in these spots, it usually dies within a year. Ground pearl infestations can be confirmed by digging in the soil where the insects live. As their name implies, ground pearl are small, round insects that are pearly white to tan in color. They look similar to the pellets of slow release fertilizer found in container-grown plants. If you suspect ground pearl in your lawn, dig into the soil three to four inches deep around the edges of dead areas, and carefully sift through the soil in your hand to find the pearl-like insects. Since ground pearl occur in clusters, be sure to check several locations before ruling ground pearl out. Infested lawnsThere are no pesticides that kill ground pearl, which are a type of scale insect. Since only turf grasses are affected, one method of dealing with them is to redesign your yard so that trees, shrubs and flowers are planted in the infested areas. On their own, ground pearl only move a few inches each year. Be very careful not to spread them around when moving soil or using tools or equipment in infested areas. The movement of soil and contaminated equipment is the main way ground pearl are spread over large areas. While all of the turf grasses grown in our area are susceptible to ground pearl, centipede is the most sensitive. Centipede lawns infested with ground pearl should be redesigned or converted to a more tolerant lawn grass. In a recent trial conducted by North Carolina State University, "El Toro" zoysia tolerated ground pearl damage better than other species in the study. Though often considered a weed, Bahia grass has also been found to be relatively resistant to ground pearl damage. Very vigorous turf grasses like "Celebration" Bermuda can be grown in ground-pearl-infested areas if they receive supplemental irrigation and fertilization. This is more effective in heavy or clay soils. In deep, sandy soils it is much more difficult to maintain a dense lawn if ground pearl are present, even when vigorous turf species are planted. Ground pearl can be found as deep as 10 inches or more in the soil and can live for 15 years or longer, even when no grass is present. Excavating large areas of soil in the hope of removing ground pearl is a very expensive and minimally effective control strategy. Any insects left behind will repopulate new soil relatively quickly since each female is able to produce one hundred or more offspring each year without mating. Excavating soil also increases the risk of spreading these pests to new areas. Other lawn problemsOther problems with symptoms that resemble ground pearl include mole crickets and large patch disease. A major difference between ground pearl and these problems is that grass will recover in areas damaged by mole crickets or large patch. Large patch shows up in the spring as rapidly expanding, circular areas of dying turf. The dying areas often appear to have a halo, with the grass on the outer edge appearing yellow or red in color. Mole cricket damage is most obvious in late summer and fall. Areas damaged by mole crickets often have an indistinct shape, with living and dead grass mixed together. The ground may be soft and churned up under the dead grass, with dead grass lying on top of the ground, disconnected from its roots. Learn moreFor more information about lawn care, ground pearl and other lawn problems, visit the N.C. Cooperative Extension's TurfFiles website at www.TurfFiles.ncsu.edu. For answers to gardening questions, visit www.cesNCSU.edu, where they will be answered by an expert. Visit the Pender Gardener blog to stay up to date with all the latest gardening news at PenderGardener.blogspot.com.